Sir William George Cusins was an English pianist, violinist, organist, conductor and composer.
He was appointed Master of the Queen's Musick by Queen Victoria in 1870, succeeding George Frederick Anderson, who had retired. He was knighted on 5 August 1892 (the only Master to be knighted during his term of office) and received the Cross of Isabella the Catholic in 1893.
Sir William Cusins produced editions of the piano music of Robert Schumann. Among his works as a composer are Royal Wedding Serenata (1863), concert overture Les Travailleurs de la mer (1869), the oratorio Gideon (produced Gloucester, 1871), overture to William Shakespeare's Love's Labour's Lost (1875), Piano Concerto in A minor, marches and songs.